Method of and apparatus for treating concrete



1 July 7,1942. R, E. DAVIS 2,289,247

METHOD OF ANDAPPARATUS FOR 'IRIEZA'IING CONCRETE Filed June 5, 1940 2Sheets-She'et l R. E. bAvls July 7, i942.

METHODOF'ANDAPPARATUS FOR TREATING CONCRETE Filed June 5, 1940 2Sheets-Sheet 2 Patented July 7, 1942 UNHT ED STAT-ES FATENT OFFICEMETHOD OF vAND APPARATUS FOR TREAT- ING CONCRETE Raymond E. Davis,Berkeley, Calif., assignor-to Kalman Floor Company, Inc, New York, N.Y., a corporation of -D elaware Application June 5, 1940, Serial No.338,991

9-Claims.

My present invention relates to methodsof and machines or implements forlaying concrete .a dense smooth-surfaced wear-resisting floor,

topping ,courses being customarily employed in the ,erection .of .manyindustrial and public buildings, the floors of which are subjected toheavy traffic.

.Numerous methods of installing topping courses have heretofore beensuggested;and .used and ,in .my copending application Serial .No.

338,992, filedrJune 5, 1940, I disclose .apreferred method by means ofwhich a topping course of improved quality can be applied to a.supporting slab or structure at less .cost and in ..less time than hasheretofore been possible byoany other known method. In accordance withthe process .describedin the applicationreferred to, a con- ;crete, mixof high water-cement ratiois first prepared, the water being present insufficient quantity toinsure high workability, thus enabling the mix tobe .quickly and easily spread over the supporting slab to therequireddepth. The freshly deposited toppingcourse is then screeded andits surface rendered approximately level. Following this a layervoffabric such as burlap is spread over :the surface ofthevfreshlydeposited concrete and a layer. of absorptive granularmaterial. such as cement or drysand, or a mixtureof cementand dry sand,is spread over the fabric. A smoothing implement is then passed back andforth over the water-absorbing powdered material, this implement beingprovided with means for effecting its vibration at a .very highfrequency, say 5,000 vibrations or more per minute. As a result of theconjoint action of the vibratory tool and the water absorptive layer ofmaterial over which it is passed, the excess water present in thetopping course is drawn upwardly and passes into the cement and sand. Inthe course of a few minutes the topping course, originally a wet orsloppy mix, can be rendered quite dry or reduced to a condition in whichits Water-cement ratio is very low, for instance approximately .25 orless by weight for mixes ordinarily employed. The burlap covering andthe sand and cement thereon are then removed and the relatively dryconcrete, which, however, has not yet .begunto set,

is subjected to the action of a rotating disc-like member which islikewise vibrated at high frequency while being revolved about avertical axis. ,The function of this last mentioned implementis tosmooth and-level the'surface While at the same time collapsing any voidswhich may possibly remain inthe concrete topping course which may havebeen caused by the rapid re- -mpval of excess-water therefrom, thusmarkedly decreasing the void space and increasing the density; of thetopping course.

The method of smoothing, leveling and finishing the surface cf theconcrete layer after it I has been rendered relatively dry, and theimplement for accomplishing this, comprise the subject matter of thepresent application, the implement being not only useful in carrying outthe process above briefly described, but being likewise useful in thesurfacing of concrete structures generally, such as floor-slabs ofordinary construction, plain andreinforc ed.

In the accompanying drawings one embodiment oftheimproved implement isillustrated in'detail, and ,will be hereinafter specifically described,but it will be appreciated'by-one skilled in the art that, minor changesin the design and arrangementof the component elements of the implementmaybe made if .desired, and that minor changes in the method to bepracticed withtheaid of the implement may likewise be made, all withoutdeparture from the teachings ofthe invention.

In. the-drawings:

Fi ral i let-persp ctiv view h w n th proved surfacing implement in theposition which yitnormally occupies when actin upon the upper surface ofaitoppingcourse;

Figure 21s a partial axial section through the implement, showing itscomponent operating elements;

Figure 1.3 isa section on line --3-3 of Figure 2;

t-Eigure 4 is a'sectiononiineA -t of Figure 3;

.and

. Figure.v 5 is ,an elevation showing more clearly certainof the detailswhich appear-in. Figures 1 and. 2.

That portion 10f; the implement which is adapted; tobearuporrthe surfaceof -a,layer of concrete, for instance .-:a; toppi-ng course, is formedas a circular; disc; 10 having, a smoothgplane or; slightly .convexundersurface. Springing upwardly; from theperiphery.v of discrlil is a.cylindrical, marginal flange l I, the ;.disc U] and flange -H togethercomprising a. h0using for: that portion of the implement which maybedesignated the vibratory unit and which, when driven, efiectsvibration of the disc at the desired rate or frequency and through thedesired distance. Supported on the shell comprising disc I and itsfiange II is a cover plate I2 and this cover plate in turn constitutesthe support for the motor casing l3 and the motor enclosed therein. Anoperating handle I4 having a bifurcated metallic member [5, or yoke, ispivotally connected to the motor casing,

as shown in Figure l, and by means of this 1,

handle the implement may be moved back and forth over the surface of aconcrete slab or topping layer. Likewise, by means of the handle,

the motor casing is held against rotation whenthe motor is energized.

It will be observed from an inspection of Figures 2, 4 and 5 that thecover plate I2 must revolve with the disc II], but at the same time isnot rigidly connected to the disc, being supported thereon for Verticalmovement by means of ings, the lower spring abutment being supported inthe position shown by a nut or by a cotter pin,

, such as indicated at 22, and the upper spring abutment 2| beingadjustably retained in position by means of a nut 23 threaded on theupper end of spindle I6. Helical compression springs 25 and 26positioned, respectively, above and below the cover plate I2 encircleeach spindle I6 and by means of these springs the cover plate isresiliently mounted upon the disc ID, both upward and downward movementof the cover plate being spring retarded.

In the operation of the implement the cover plate is revolved by themotor and in turn drives the flanged disc I0. The disc is vibrated athigh frequency by means to be hereinafter described but the connectionbetween disc and cover plate must be such that that plate, the motormounted thereon and the handle do not comprise portirns of the mass tobe vibrated. For this reason the springs 25 and 26 are provided andlikewise rubber bushings I8 are fixed in openings IS in the cover plate,these bushings encircling spindles I6 and transmitting the drivingtorque of the motor to the driven disc II] but damping or absorbing thevibratory movements of the disc and spindles I6 so that such movementsare not communicated to the motor.

The motor housing I3 encloses the stator and rotor of an electric motor(not shown) and the rotor thereof is mounted upon a hollow motor shaft30 which projects downwardly through the bottom of the motor casing andlikewise downwardly through the cover plate I2. Fixed upon shaft 30 justbelow the cover plate I2 is a driving plate or friction disc 32 andloosely mounted on shaft 30 just below disc 32 is a pulley 33 in theperiphery of which is formed the V-shaped groove 33' which receives adriving belt. Pulley 33 rests upon a thrust bearing 34 which is mountedupon a disc 35 attached to the lower end of a rod 36 which extendsvertically upwardly from a point below the disc 34, through the hollowmotor shaft, to a point well above the top of the motor casing, as shownin Figures 2 and 6. The top of the rod 36 has a head 36 rigid therewith,the

motor and pulley.

head 36 functioning as an abutment for the upper end of the compressionspring 31 which normally urges rod 36 upwardly. The quadrantlikeeccentric 40 is positioned to act upon the upper end of rod 36 and toeffect depression of the rod when desired.

The effect of the compression spring 31 is to maintain, acting throughrod 36, the upper surface of pulley 33 in frictional engagement with thelower surface of driving disc 32 and to thereby maintain a drivingconnection between pulley 33 and the motor. The eccentric 40, however,may be moved to force downwardly rod 36 against the action of spring 31and thus allow pulley 33 to fall away from the friction disc 32, thusinterrupting the driving connection between the It will be observed thatthe eccentric 40 is mounted upon the shaft 42 and is in fact fixed uponthis shaft, which shaft is supported in a bearing formed in the upperend of a bracket 43 integral with the motor housing. Likewise fixed onshaft 42 is a small pulley or grooved wheel 44 over which passes anendless belt or cord 45 extending to and around a small grooved wheel orpulley 46 mounted upon the handle I4 and adjacent the cross-piece 4!which the operator grasps to manipulate the implement. By pulling onereach or the other of belt 45 the short shaft 42 may be revolved ineither direction as desired, thus rocking the eccentric in the desireddirection and making or breaking the driving connection between thefriction disc 32 and the pulley 33 at the will of the operator. Movementof the eccentric is limited to an angle of approximately by contact ofstops 40' with top of rod 36. Other means for operating rod 36 may beemployed if desired, for instance a solenoid operated cam may besubstituted for pulley 44 and cam 40.

Encircling pulley 33 is an endless belt 48, this belt passing over guidepulleys 49 and downwardly and around the grooved pulley 50 fixed on theend of eccentric shaft 5I. Shaft 5| is mounted in a plurality of alignedbearings 52 mounted on supporting pedestals 52', the bearings beingpreferably of the ball or roller type. The protuberances 5| as shown inFigure 2, comprise eccentric weights integral with shaft 5|, the shaftbeing so designed, with respect to the mass and eccentricity of theseeccentric weights that when revolved at the desired speed the disc It]will be vibrated at the desired high frequency and through the desireddistance. Naturally the weight or mass of the eccentric portions 5| ofthe shaft is calculated or established so as to have a specificrelationship to the weight or mass of the disc I6 and all parts rigidtherewith, in known manner. The motor and cover plate, however, whilesuperposed upon the disc and tending to press the disc down tightly uponthe concrete surface are nevertheless not vibrated at high frequency bythe action of the eccentric means just described, the resilient meansinterposed between the motor and cover plate acting to absorb vibrationsof small amplitude.

During the'time that the motor is in operation and the pulley 33clutched to the disc 32 so that the vibratory shaft 5| is rotating, theentire assembl including the disc ID, the vibratory unit supportedthereby, and the cover plate I2, is revolved about the axis of the motorshaft but at a relatively low speed. Thus the motor shaft is shown tohave mounted thereon a pinion 66, the teeth of which mesh with those ofa gear 6I mounted on the short shaft 62, which shaft is supported inbearings 63 and 64. Shaft 6.2 has fixed thereon a pinion 65 the teeth ofwhich mesh with those of a gear 66 which is mounted upon the upper endof a sleeve 51 encircling the motor shaft but not connected thereto inany way. The lower end of sleeve 61 is attached to the upper surface ofthe cover plate by means of screw bolts 10 and in annular recessesformed in the upper and lower ends of sleeve 61 are housed bearings IIand H which function to maintain the sleeve and motor shaft in trueco-axial relationship and reduce possible friction between thecontiguous surfaces of these elements, which are naturally rotating atdifferent speeds. By gearing just described, motion is transmitted fromthe motor shaft to the entire lower assembly comprising disc ID with itsflange H and cover plate l2, with all attached parts, but the gearing isfashioned as a reduction gearing so that the disc I is revolved aboutits axis at a relatively low speed as compared with the speed ofrevolution of the shaft shaft 5| being revolved at considerablyhigher-than-motor speed.

It is clear that, by manipulating the clutch the vibratory unit may becalled into operation or rendered inoperative as desired. In certaininstances it may be desirable to use the implement to perform only thefunctions of the rotary float of well-known type. However, the vibratoryunit will be employed whenever the implement is used in the practice ofthe process for which it has been primarily designed, i. e., thesurfacing of a body of semi-solid material such as unhardened concretewhich is of such dry consistency or of such low water-cement ratio that1 the ordinary rotary float now commonly used for this purpose cannotsuccessfully function. With the disc simultaneously rotating andibrating at high frequency there is imparted to a very dry mix a plasticcondition, enabling rapid and successful surfacing and compaction of thetopping, interior voids being closed, high areas of the surface lowered,and low areas raised. The surfacing is largely accomplished, not bylaterally displacing or pushing concrete but by effecting verticalmovements of certain portions of the concrete with respect to otherportions. The resulting concrete structure is denser and moresatisfactory than others which have not been subjected to the action ofthe implement in question and considerable time is saved in thesurfacing, the necessity for much of the troweling ordinarily requiredbeing obviated.

When the implement is in actual use in the surfacing of the dry mix eachportion of the disc M] will be vibrated, but not only in a verticaldirection. In facteach point on the lower surface of the disc will movein a closed curved path in planes normal to the axis of the eccentricshaft 5!. Hence the surface of the concrete will be subjected to akneading action of high frequency, as well as a smoothing action. It isimmaterial whether the concrete topping layer which is worked with theaid of the implement described is originally mixed with a highwatercement ratio, and then dewatered, or is a dry stiff mix to beginwith, so far as the surfacing operation is concerned. In either case thenovel implement is employed to level the surface of the floor slab ortopping course to which it is applied and to raise to the surface asmall amount of paste for final troweling. Preferably the consistency ofthe mix is such that, after the vibrating and rotating implement ispassed over iii its surface once or twice the surface is level and thereis brought to the surface a barely perceptible film of a very stiffsand-cement paste which may be immediately finished in one or two handtroweling operations. Maximum economy of labor is thus effected and muchtime saved. The resulting floor slab or topping layer is also denser,harder and more resistant to abrasion.

Having thus described the invention, what is claimed as new and desiredto be secured by Letters Patent is:

1. An implement for surfacing concrete floors comprising a disc adaptedto rest upon the surface of a relatively dry mass of fresh concrete,means for revolving the disc about an axis, and means for vibrating thesame in horizontal, vertical and inclined directions at high frequencywhile rotating.

2.'In an implement of the class described, in combination, a drivingmotor having a rotor and easing, a disc below the motor and having asubstantially fiat concrete working lower surface and an eccentricmounted upon the disc for rotation about an axis parallel to the planeof the disc, a driving connection between the rotor of the motor and thedisc which includes resilient means permitting relative verticalmovements of motor and disc and whereby the disc may be rotated by themotor about a vertical axis, and a driving connection between the rotorand said eccentric whereby the eccentric may be rotated about ahorizontal axis while the disc is revolving.

3. The combination set forth in claim 2 in which the driving connectionto the eccentric includes a flexible driving member which permitsrelative vertical movements of motor and eccentric.

4. The combination set forth in claim 2 in which the driving connectionto the eccentric includes a clutch whereby such driving connection maybe established or broken at the will of the operator.

5. The combination set forth in claim 2 in which the driving connectionto the rotating disc includes a speed reduction gearing.

6. The combination with a disc for acting upon the surface of a plasticmass, of a motor, means operatively connecting the disc and motorwhereby the disc will be rotated when the motor is energized, aneccentric rotatably supported on the disc and rotatable with the disc,and means operatively connecting the motor and eccentric.

7. The method of surfacing and compacting a body of concrete which is ofsuch dry consistency and in such stable or solid condition that itcannot be surfaced by horizontally displacing the particles of theuppermost stratum thereof, which comprises subjecting each area of theupper surface of such body to the pressure of a surfacing implementhaving a fiat work-engaging surface and, while maintaining suchpressure, simultaneously revolving said surface about an axis normalthereto, advancing the same laterally, and vibrating it at highfrequency.

8. The method of surfacing and compacting a body of concrete which is ofsuch dry consistency and in such stable or solid condition that itcannot be surfaced by horizontally displacing the particles of theuppermost stratum thereof, which comprises moving over the surface ofsuch body a member the work-engaging surface of which is revolving aboutan axis normal to its working face and also vibrating at high frequency.

9. The method of surfacing and compacting a body of concrete which is ofsuch dry consistency and in such stable or solid condition that itcannot be surfaced by horizontally displacing the particles of theuppermost stratum thereof, which comprises subjecting each area of theupper surface of such body to the pressure of a circular disc having afiat work-engaging surface and, while maintaining such pressure,simultaneously rotating said disc about an axis passing throughitscenter and normal to its working surface, advancing the same laterally,and. vibrating it at high frequency.

RAYMOND E. DAVIS.

